Adjustable bridges

Forgive me if this has been asked before, as I am new to the double bass forum.

Recently I purchased and received a 3/4 size upright bass. I also order an adjustable bridge, due to not liking the action being high, and a 3/4 gig bag. My question is, why do upright basses not come shipped already with an adjustable bridge?

Some luthiers think that adjustable bridges inhibit the sound, but without a spectrograph (I think?) no one can really tell unless they have crazy good hearing and have never been right in front of the timpani in an orchestra .